Energy Converter

Convert between joules, calories, kilowatt-hours, BTU, electron volts, and other energy units.

Joules are the common currency, and the default entry of one kilowatt-hour is the clearest illustration of why the spread of units exists at all: the same quantity of energy is 3.6 million joules, 860.42 kilocalories and 3412.13 BTU depending on which trade is asking. The Joules row behaves unlike the others — it is a text field, because once the figure passes a million the engine switches to exponential notation, so a kilowatt-hour prints as 3.6000e+6 rather than a long string of digits. Read the Kilocalories row as the dietary Calorie with a capital C, stored at 4184 joules, which is a thousand of the small calories a chemist means. Both the small calorie and the electron volt can be selected on the way in, but neither has a column of its own on the way out, and the electron volt factor is held at 1.602e-19 joules against the exact 1.602176634e-19 fixed by the SI redefinition of the elementary charge — a rounding of roughly one part in ten thousand that matters only in particle work. No time appears anywhere in this engine, so it cannot give you power in watts, tell you what a load draws, or apply an efficiency. It also has no tariff, so converting a kilowatt-hour will not price it, and there is no natural-gas therm or CCF among the selectable units.